water pump not priming UPDATED PROBLEM FIXED

Is your water tank below the pump? Mine is and the pump won't prime easily unless the tank is filled right up it the overflow hole beside the fill hole, which is a little above the pump. Similarly, it is hard to start the pump pulling antifreeze out of a jug. I keep a dish detergent squirt bottle handy to fill the hose and pump with water or antifreeze to make it start easily. I guess my water pump just doesn't pump air well. I don't know if it is worn or just the nature of the beast. No problem once it is primed. I will try to remember to look for an inlet screen to clean.

Just remembered, when winterizing I loosen the pump fitting on the inlet tube, letting air in to allow the water in the hose to drain down into the tank. If I forget to tighten it up again, the pump sucks air.